I have a 740 Gle N.A. with 185K. The car would sometimes cut out while driving. I suspected that it was electrical so I ran a wire from the main fuel pump to a small bulb, one from the fuel pump relay to another bulb and one from the ignition coil to a third bulb. Then I grounded all neg. wires together and mounted bulbs on a small board inside car where I could observe that these three devices were working. Theory being if the car cut out while driving and one of the bulbs was temporarily not lit then that would give me a starting point for troubleshooting. Drove the car for several days and of course engine did not cut out and bulbs remained lit. Here's where the real trouble begins. This past weekend I replaced the O2 sensor with the "universal" 02 sensor. Took it for a short 5 minute drive to make sure everything was ok and as I was heading back home the car suddenly died and would not restart. Checked the fuses and found #1(main fuel pump) fuse blown. Replaced fuse and attempted to start, #1 fuse blows again. I then remove all the "test bulbs" just to make sure, still blows #1. Spent all weekend isolating wires and finally found what I thought was the culprit. Fuel injector relay has two wires going into terminal 87/2. One is a pink wire that goes to the fusebox, the other is a green one that according to my Hayne's wiring diagran goes to my 02 sensor. I found that if I disconnect the green wire from the sensor I still blow the fuse. If I remove the green wire from the relay and still leave the pink one attached then I can crank all day, car won't start BUT #1 fuse does not blow either. My mind is mush from working on this for three straight days. I do not think I hooked up the sensor wrong. Three wires, one black, two white. Black one goes to green wire, Right? Sorry this post is so long. Any ideas would be most welcome.